Electric circuit breaker



Jan. 31, 1933. E. B. MERRIAM ELECTRIC CIRCUIT BREAKER Filed Aug. 26, 1951 Inventor: EZT'a B. Merriam bg His Attorney.

'1' the switch tank.

Patented Jan. 31, 1933 UNITED STATES PATENT OFFICE EZRA B. MERRIAM, OF SWARTHMORE, PENNSYLVANIA, ASSIGNOR TO GENERAL ELEC- TRIC COMPANY, A CORPORATION OF NEW YORK ELECTRIC CIRCUIT BREAKER Application filed August 26,1931.

M invention relates to electric circuit breakers, more particularly to electric switches of the fluid break or oil type, and has for its object the provision of an improved fluid break switch which shall have increased interrupting capacity and which shall be simple, rugged and inexpensive 1n construction.

In accordance with my invention a switch tank containin an insulating liquid, as oil,

is provided wit one or more, preferably two, lateral pockets or chambers forming restricted vents adjacent and opposite coacting switch contacts immersed in the oil within Upon opening movement of the switch contacts the corresponding are drawn opposite and substantially at the entrance of a lateral chamber is urged by magnetic and other forces towards the interior of said chamber, the resulting pressure generated by the are within the restricted area of the chamber causing a so-called explosion chamber effect to interrupt the arc.

My invention will be more fully set forth in the following description referring to the accompanying drawing, and the features of novelty which characterize my invention Wlll be pointed out with particularity in the claims annexed to and forming a part of this specification.

Referring to the drawing, Fig. 1 is an elevational view, partly in section, of an electric circuit breaker embodying my invention and Fig. 2 is a cross-sectional plan View taken along the line 22 of Fig. 1.

The circuit breaker shown in Fig. 1 comprises certain features of a fluid break or oil switch of the conventional type including a pair of stationary contacts 1 interconnected in the closed circuit position illustrated by a conducting bridging member 2, the contact structure being disposed within a switch tank 3 and immersed in an arc extinguishing or insulating liquid 4, as oil, contained therein. The switch contact structure may be of any suitable type and in the present instance the bridging member 2 is connected to and operated by the lift rod 5 extending through and guided by the switch tank cover 6 for vertical movement. The stationary contacts 1 are Serial No. 559,511.

supported at the lower ends of the insulating bushings 7 extending through and mounted on the cover 6 and are electrically connected to the lead-in conductor studs 8 extending through the bushings 7. The circuit breaker so far described is of the conventional type except for the fact that the coacting contact surfaces are generally spaced a greater distance than shown from the side walls of the tanks, the opening and closing operations of the switch being effected merely by lowering ang raising the bridging member 2 by the r0 5.

In the operation of a so-called plain break alternating current oil switch wherein the bridging member simply separates from the coacting stationary contacts within a body of oil, the interrupting action is more or less fortuitous in View of the fact that the gas bubble formed in the oil and which serves as a conducting medium for the arc, is finally broken up and displaced by oil mainly by the turbulence caused by the arc, and not by positive means. In interrupting an alternating current circuit an oil switch interrupts when the current is passing through the zero value of the cycle thereby indicating that sufficient dielectric is interposed between the contacts at the zero point of the cycle to prevent reestablishment of the current. During circuit interruption the arc is generating pressure at a high rate when the current is at the maximum value of the cycle, the rate decreasing as the current approaches the zero value. However, when the current has reached the zero value the pressure generated in a plain break switch during the previous part of the cycle is of little aid in positive interruption of the circuit since the energ is freely dissipated in all directions wit in the oil body.

For the purpose of more effectively and positively interrupting the current within a comparatively brief arcing period and for utilizing the pressure generated during arcing, the tank 3 is provide-d with a pair of lateral pockets or restricted chambers 9 formed by the wing-like metal extensions 10 welded or otherwise suitably oined to the steel tank 3. In the embodiment illustrated the lateral chambers 9 are restricted in cross sectional extending through slots in the lining 11 to form are receiving extensions of the chambers wlthin or at the entrance of w-hlch the coacting contact surfaces of the stationary contacts 1 and the bridging member 2 are disposed. The insulating linings l1 and 12 may be of suitable insulating material in sheet form, asa compound including a phenolic condensation product.

Accordingly, when the bridging member 2 is lowered the arcs drawn substantially transversely of an at the openings of the restricted lateral chambers 9 are urged by magnetic forces of the current traversing the U-shaped loop through the switch further into the corresponding chambers. Immediately upon separation of the contacts the heat of the re sulting arcs generates high pressure in the region of the contacts forming the well known gas bubble which is highly conducting and sustains the are; In the present instance the arc is bowed or looped into the adjacent restricted chamber so that the pressure formed thereby tends to force oil mainly in one direction, that is from the chamber into the main oil body, as in the well known explosion chamber. During the higher values of the current the gas bubble maintains itself within the lateral chamber due to the fact that additional gas is constantly being generated at ahigh rate by the heat of the arc. When the current reaches the zero part of the cycle,

however, the rate of gas generation has accordingly decreased, thereby afiording the best opportunity to interrupt the circuit. Since the pressure generated within the restricted chamber represents a certain amount of stored energy which is effective to force oil and gases at high velocity out of the pocket to cut oif the arc the circuit is interrupted .due to explosion chamber effect at the zero part of the cycle. A circuit breaker so con- I structed in accordance with my invention not essary the size of the switch tank may be reduced by providing a single pocket at but one ofthe breaks. It is furthermore apparent that the oil within the switch tank need not completely fill the lateral pocket. In other words, the upper part'of the pocekt may be designed to form an air cushion, instead of utilizing the space above the oil level in the main tank, the lateral extension in this instance being provi-ded likewise with an oil and gas bafile, as of the well known pebble type for freely venting gases and preventing appreciable discharge of oil from the switch.

It should be understood that my invention is 'not limited to specific details of construc tion and arrangement thereof herein illustrated, and that changes and modifications r may occur to one skilled in the art without departing from the spirit of my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is: 1. An electric circuit breaker comprising relatively movable coacting contacts, and a tank containing insulating liquid in which said contacts are immersed, said tank provided with an extension forming a narrow lateral pocket opposite and adjacent said coacting contacts, said pocket being restricted in cross sectional area as compared with said tank and arranged so that the are formed upon separation of said contacts is drawn transversely of the opening of said pocket.

2. An electric circuit breaker comprising a tank containing insulating liquid, and a pair of stationary contacts connected in the closed circuit position by a bridging member immersed in said liquid, said tank provided with wing-like extensions forming pockets restricted in cross-sectional area as compared with said tank, the opening of each pocket being opposite and adjacent a fixed contact and said bridging member so that the are drawn upon opening movement of said bridging member is substantially transversely of and at the entrance of said pocket.

3. A circuit interrupter comprising a tank containing oil, relatively movable coacting contacts including a bridging member immersed in said oil, said tank provided with lateral wing-like extensions forming najrzrow restricted pockets at opposite side's of said tank, each of said pockets filled with cit-and opening into said tank substantially;atthe point of separation of a pair of coacting contacts, and an insulating liningrfor each of said pockets forming the opening of the pocket in which the corresponding arc is drawn. I

4. In an electric circuit breaker including coacting contacts separable within an are extin guishing liquid, a switch casing containing said liquid provided with a lateral'extension forming a pocket, said pocket being restricted in cross sectional area as compared withsaid casing, said coacting contacts positioned substantially at the entrance of said pocket so that an are formed upon separation of the same is drawn transversely of the opening of said pocket.

I11 witness whereof, I have hereunto set 

